I. Field of the Invention
The present invention generally relates to devices for treating various medical conditions and, more particularly, relates to occlusion devices for treating various target sites within a patient's body.
II. Description of the Related Art:
A wide variety of intracardiac prosthetic devices are used in various medical procedures. For example, certain intravascular devices, such as catheters and guide wires, are generally used to deliver fluids or other medical devices to specific locations within the vascular system of a patient, such as a selective coronary artery. Other devices are used in treating specific conditions, such as devices used in removing vascular occlusions or for treating septal defects and the like. For example, devices have been developed for treating abnormalities, such as an Atrial Septal Defect (ASD), a Ventricular Septal Defect (VSD), a Patent Ductus Arteriosus (PDA), a Patent Foramen Ovale (PFO), a Left Atrial Appendage (LAA), an Arterial Venous Malformation (AVM), as well as conditions that result from previous medical procedures such as Para-Valvular Leaks (PVL) following surgical valve repair or replacement.
Generally, a PFO is a condition where an abnormal opening is present in the septal wall between the left and right atria. In particular, the PFO typically has a tunnel passageway extending between the right and left atria that is defined between the atrial septum and the PFO flap. Under certain conditions, such as when a person coughs, the pressure in the right atrium can rise above the pressure in the left atrium causing blood to momentarily flow from the right atria to the left atria. In some patients, blood clots may collect in the PFO or near the right atrial PFO opening. Blood flowing from the right to the left atria through the tunnel opening may carry a blood clot into the left atrium. If such a clot were to flow to an artery in the head, a stroke may occur when the blood clot obstructs blood flow to the brain. It is also suggested that migraine headaches may be related to the existence of a PFO. Closing a PFO may prevent or reduce the risk of a stroke and may reduce the frequency or intensity of migraine headaches. The PFO abnormally tunnel shaped opening normally does not extend perpendicularly through the septal wall, but is oriented obliquely to substantially parallel to the atrial septum. Devices have been developed to occlude the tunnel by employing a pair of closely spaced interconnected disks that are configured to be disposed within the left and right atria on either side of the tunnel. However, because the PFO tunnel lies in an oblique plane with respect to the openings of the tunnel, the disks may be urged into coaxial alignment with one another, which may distort the PFO tunnel walls causing the PFO flap to lie in other than a flat plane. This distortion of the PFO flap makes for a more challenging opening to seal. Various designs have been proposed to account for closing a PFO tunnel and PFO distortion. One such design is one having an elastic elongated central member that extends through the PFO tunnel length, connecting and urging the disk members on either side of the atrial septum toward each other to occlude the PFO. Although this design allows for the variation in tunnel length and eccentricity of the openings, the clamping force is applied in line with the tunnel as opposed to direct clamping more perpendicular to the disks. As a result, some distortion of the PFO flap may occur. In such a design, the clamping force is determined by the configuration of the elastic central member, the wire diameter, and number of wires.
Accordingly, it would be advantageous to provide a medical device that is both easy to deploy through a lower profile catheter and that can be accurately placed in a target site, such as a PFO with minimal distortion of the PFO flap or tunnel, while providing improved clamping force for a more effective seal and fixation. It would also be desirable to have a medical device having a softer sealing surface to minimize atrial/septum tissue abrasion while still providing adequate clamping forces. It would also be advantageous to have a medical device design that allows for selective clamping force at selective locations about a target site, such as the PFO. In addition, there exists a need for a medical device for occluding a target site that provides rapid occlusion following delivery and placement thereof.